Sickle cell disease is caused by inheriting the sickle cell gene.
It's not caused by anything the parents did before or during the pregnancy and you cannot catch it from someone who has it.
Genes come in pairs. You inherit 1 set from your mother and 1 set from your father.
To be born with sickle cell disease, a child has to inherit a copy of the sickle cell gene from both their parents.
This usually happens when both parents are "carriers" of the sickle cell gene, also known as having the sickle cell trait.
Or it can happen when 1 parent has sickle cell disease and the other is a carrier of it.
Sickle cell carriers do not have sickle cell disease themselves, but there's a chance they could have a child with sickle cell disease if their partner is also a carrier.
If both parents are sickle cell carriers, there's a:
The Sickle Cell Society has more information about the inheritance of sickle cell disease, including what the risks are if a parent has sickle cell disease themselves.
In the UK, sickle cell disease is most commonly seen in people of African and Caribbean backgrounds.
A simple blood test will show whether you're a carrier. This is done routinely during pregnancy and after birth, but you can ask to have the test at any time.
Your genes are the set of instructions found inside every cell in your body. They determine characteristics like the colour of your eyes and hair.
People with sickle cell disease do not make haemoglobin properly. Haemoglobin is a substance in red blood cells, which carry oxygen around the body.
Normal red blood cells are flexible and disc-shaped, but in sickle cell disease they can become rigid and shaped like a crescent or sickle because the haemoglobin inside them clumps together.
These unusual cells can cause symptoms of sickle cell disease because they do not live as long as normal red blood cells and can become stuck in blood vessels.